Downstream microwave plasma-enhanced chemical vapor deposition of oxide using tetraethoxysilane

Abstract

In this paper, results for dielectric oxide films deposited using downstream microwave plasma-enhanced chemical vapor deposition in the temperature range between 250 and 400 °C are presented. The deposition of oxide using TEOS (tetraethoxysilane)+O2 and TEOS+N2O chemistries are studied. In the reactor, the TEOS is injected directly into the deposition chamber without passing through the discharge. Only He, O2, or N2O are fed through the microwave cavity where the discharge is generated. In addition, no ions but chemically active species are present in the deposition chamber during the deposition. The deposition rate is found to decrease with increasing temperature. In addition, it appears that the deposition rate increases with increasing concentration of active oxygen species in the deposition chamber. These suggest that the generation of intermediate species of TEOS and adsorption/desorption of the reactant on the surface are the key steps that determine the deposition rate. The stress of the deposited oxide films is found to be tensile and less than 2×109 dyn/cm2. The Si-OH concentration in the films is found to be low and can be below the detection limit of infrared spectrometry by increasing the flow ratio of O2/TEOS during the deposition. The step coverage of the oxide films over the Al runners is found to be excellent due to the long diffusion time available for TEOS surface species before forming SiO2. The mechanisms of oxide deposition using TEOS+O2 and SiH4+N2O chemistries are studied and compared. The details of oxide step coverage versus different deposition processes are also discussed.